Magnetic disk drives are used to store and retrieve data in many electronic devices including computers, televisions, video recorders, servers, digital recorders, etc. A typical magnetic disk drive includes a head having a slider and a transducer with a read and write element that is in very close proximity to a surface of a rotatable magnetic disk. As the magnetic disk rotates beneath the head, a thin air bearing is formed between the surface of the magnetic disk and an air bearing surface of the slider. The read and write elements of the head are alternatively used to read and write data while a suspension assembly positions the head along magnetic tracks on the magnetic disk. The magnetic tracks on the magnetic disks are typically concentric circular regions on the magnetic disks, onto which data can be stored by writing to it and retrieved by reading from it.
As the magnetic disk rotates beneath the head, a head gimbal assembly located on the suspension assembly is used to position and orient the head at the correct height above the magnetic disk while in flight. The suspension assembly includes a load beam and the gimbal assembly that attaches the head to the load beam. The gimbal assembly includes a flexible circuit that is used to deliver electrical signals and power to the head and other electronics located on the end of the suspension assembly. The flexible circuit is split into a left electrical trace that and a right electrical trace that follow a left outrigger and a right outrigger. The left and right outriggers are used to support the flexible circuit and head and to attach the flexible circuit and head to the load beam. Conventional magnetic disk drives use a single-tether gimbal assembly wherein the flexible circuit assembly is connected to the outriggers by attaching the left electrical trace to the left outrigger at a single point and by attaching the right electrical trace to the right outrigger at another single point.
During operation of the magnetic disk drive, the magnetic disk is made to rotate at very high revolutions per minute (rpm) that can be well in excess of 10,000 rpms. At these very high speeds the suspension assembly can be subject to forces and resonances that can significantly impact the gimbal assembly as well as the entire magnetic disk drive. Force example, these forces can cause the flexible circuit to distort or solder bonds to fail, or both. Further, if a flexible circuit is sufficiently distorted then a large enough pitch static angle can be created that changes the orientation of the head. These forces and resonances can make the gimbal assembly unstable and sensitive to head disk interface forces. These sensitivities can cause the magnetic disk drive to be unreliable, slow and can reduce the lifetime of the magnetic disk drive.
As magnetic disk drive technology advances, acceptable engineering tolerances are made more stringent and operating conditions become more severe. For example, as magnetic disk drive technology advances magnetic disk drives are designed to operate at higher and higher speeds. At these higher speeds, components within the magnetic disk drive are subjected to new forces and different resonances which were not present before at lower speeds. Further as magnetic disk drives evolve and tolerances become tighter, forces and resonances present within magnetic disk drives that could once be ignored because they were small, are no longer small and can no longer be ignored. The single-tether gimbal assembly, which has been used in conventional magnetic disk drives, worked well with older technology magnetic disk drives were certain resonances and forces were not a concern. However, with new magnetic disk drives operating under tighter tolerances than in the past, magnetic disk drives that employ conventional single-tether gimbal assembly experience significant resonances and forces resulting from the head disk interface which is impacting the performance and reliability of the magnetic disk drive
Therefore, what is needed is a system that reduces the sensitivity of the magnetic disk drive to forces and resonances resulting from the head disk interface which has direct impact on the long-term reliability of the magnetic disk drives.